This invention relates to a semiconductor structure and fabrication process and more particularly to techniques for forming a structure that provides adhesion between silicon dioxide and titanium.
During semiconductor fabrication it is common to use silicon dioxide (SiO2) as an insulator between metal layers due to its superior dielectric properties. It is typical to form a titanium/aluminum/titanium (Ti/Al/Ti) stack for use as a metal1 layer. Over this metaI1 stack a thick film of plasma SiO2 is deposited. Usually before a metal2 layer is deposited on the dielectric, topography variations existing on the dielectric are smoothed out by planarization techniques such as chemical-mechanical polishing (CMP).
Unfortunately, the polishing technique by its very nature induces a lot of stress at the interface between the metal1 layer and the dielectric layer. Extensive peeling of the dielectric is observed if the adhesion between the metal and dielectric is poor, which is highly undesirable.
The present invention addresses the poor adhesion that can exist between a metal layer and a dielectric layer in the several embodiments described hereinafter.
A first embodiment of the present invention is a structure having a silicon dioxide film bonded to a metal film comprising:
a metal nitride film bonded to the metal film; and the silicon dioxide film bonded to said metal nitride film.
The structure of the first embodiment is formed by a semiconductor fabrication process for adhering silicon dioxide to metal comprising the steps of:
cleaning the surface of the metal;
converting the cleaned metal surface to a metal nitride; and
forming silicon dioxide subjacent to the metal nitride.
A second embodiment of the present invention is a structure having a silicon dioxide film bonded to a metal film comprising:
a metal oxide film bonded to the metal film; and
the silicon dioxide film bonded to the metal oxide film.
The structure of the second embodiment is formed by a semiconductor fabrication process for adhering silicon dioxide to metal comprising the steps of:
cleaning the surface of the metal;
forming an oxygen deficient film on the metal surface; and
forming a silicon dioxide layer over the oxygen deficient film, thereby causing a chemical reaction between the oxygen deficient film and the metal to form an interfacial metal oxide bonding layer therebetween.
A third embodiment of the present invention is a structure having a silicon dioxide film bonded to a metal film comprising:
a metal/oxide/nitride film bonded to the metal film; and
the silicon dioxide film bonded to the metal/oxide/nitride film.
The structure of the third embodiment is formed by a semiconductor fabrication process for adhering silicon dioxide to metal comprising the steps of:
cleaning the surface of the metal;
converting the cleaned metal surface to a metal nitride;
forming an oxygen deficient film on the nitrided metal surface; and
forming a silicon dioxide layer over the oxygen deficient film, thereby causing a chemical reaction between the oxygen deficient film, the metal nitride and the metal to form an interfacial metal/oxide/nitride bonding layer therebetween.